A service level agreement is a business agreement between a client and a provider of communication or computer network capacity. Traditionally, such agreements have specified a minimum bandwidth to be provided in connection with ATM/frame relay technology. However, such agreements have not typically been used in connection with Internet protocol networks.
With the development of new Internet protocol technologies, such as differentiated services (DiffServ), contracts between clients and network serviced providers are more likely to specify minimum quality of service levels in connection with Internet protocol networks. For example, a service provider may guarantee that traffic marked with the DiffServ Expedited Forwarding code points will take less than 50 milliseconds to transit the network with less than 0.1% of the packets being dropped, provided that less than 10% of the traffic is marked with an expedited flag.
In the event that the perceived quality of network service is less than the guaranteed levels, it will be necessary for the client to audit the actual service levels provided by the network. This must be done in a reliable and unobtrusive way in order to establish that the service provider is not meeting the terms of the agreement, or to identify other potential sources for the perceived quality deficit. In addition, it would be desirable to provide a way to determine whether the actual service levels provided by an Internet protocol network requires that data packets be marked with an expedited flag, potentially incurring additional cost for the transmission of those packets, in order to ensure delivery of such data packets within desired performance parameters.
Prior art solutions for auditing network service levels are only capable of auditing ATM or frame relay networks; they are incapable of auditing Internet protocol networks. Furthermore, prior art auditing solutions measure the quality of service from end to end, rather than within or across the network region governed by a service level agreement. Measuring the end to end performance available between communication end points does not provide an acceptable way to audit the performance of a service provider network, because a measurement of end to end performance typically includes the effects of the customer's network at one or both ends of the communication.